Silent Knight. Deep Six Security Series, #7

Thomas Griffin never thought he'd be a homeless vet at forty-six years old. But when he was no longer useful to the government he'd spent his life serving, they turned their back on him when he needed them most, costing him everything he ever loved. After that, he really didn't care. Living his life on the fringe was safe and he didn't have to worry about anything except his next meal. That safety remains until a beautiful socialite decides to come slumming for Thanksgiving on the wrong side of town and gets herself into trouble.
Over her fifty-five years of life, Lou Ellen Wells had received many blessings. To pay them forward and honor the men in her life who served her country, both living and dead, she cooked Thanksgiving Dinner at the Dallas Veteran's Services Center every year. It was located in a bad part of town, but she'd never had a problem, until this year when she's brutally attacked and can't get to her gun. A bedraggled man with piercing blue eyes jumps to her rescue and saves her with moves out of an action movie.
She gives him her card and offers him help, but he tells her doesn't need saving and takes off like his tail is on fire. A couple of weeks later, Lou is surprised when the man calls her asking for help of a different kind. A teenage girl he cares about has gone missing in gang territory. He's afraid she'll get killed if he doesn't find her soon. Lou calls in the team to help him, but her price for that help is finding out why her Silent Knight, who is obviously skilled and educated, chooses to be homeless. But will satisfying her curiosity about Thomas Griffin put her in the crosshairs of a terrorist group even more dangerous than MS-13?